Polyamides are well known commercial polymers wherein the structural units are linked by amide groupings (CO--NH) or (CO--R--NH).
Some polyamides are known for their fiber-forming ability, such as those called by the sub-generic term "nylon" which are represented by the structure ##STR1## where R and R' represent, independently, one or more methylene groups and n is a plural number commensurate with, or indicative of, the molecular weight. These nylon resins are prepared by polymerizing a diamine with a diacid; nylons 6/6, 6/9, 6/10, and 6/12, e.g., belong in this classification.
Other nylons, e.g., nylons 6, 11, and 12 are prepared by polymerizing amino acids or amino acid derivatives. The highly commercialized nylon 6 is polymerized from the 6-carbon amino acid derivative, caprolactam: ##STR2##
Other polyamides, known as poly(amide-imide) are polymers based on reactions of tremellitic anhydride with aromatic diamines. Whereas nylons are all polyamides, not all polyamides are nylons.
It is within the purview of the presently claimed invention, to employ, as a starting material of the blend, any normally solid, substantially uncrosslinked polyamide which contains, as recurring groups, an amine nitrogen attached to a carbonyl. A convenient reference for further general information about nylons and polyamides is MODERN PLASTICS ENCYCLOPEDIA published recurringly by McGraw-Hill. The MERCK INDEX contains a limited amount of information about "nylon".
The ethylene/carboxyl containing copolymers used in the present invention are commercially available, especially those of the type known as "interpolymers", but may also be of the type known as "graft copolymers" and "block copolymers". These expressions are known to practitioners of the art. Interpolymers are made by polymerizing a mixture of the monomers; graft copolymers are made by grafting olefin acid groups onto a polyethylene chain; block copolymers are those wherein long polymer chains comprise chain segments of a polymerized plurality of ethylene units and segments of a polymerized plurality of the carboxyl-containing monomer units.
As used herein the expression "olefin acids" refers to olefinically-unsaturated carboxylic acids which are copolymerizable with ethylene, especially acrylic acid, methacrylic acid, crotonic acid, and 1-butenoic acid, most especially acrylic acid and methacrylic acid.
Patents which disclose interpolymerizations of ethylene and unsaturated carboxylic acids in a steady state reaction at high temperature and high pressure in a stirred reactor in the presence of a free-radical initiator are, e.g., Canadian Pat. No. 655,298 (and its U.S. counterpart U.S. Pat. No. 4,351,931): U.S. Pat. No. 3,239,370; U.S. Pat. No. 3,520,861; U.S. Pat. No. 3,658,741; U.S. Pat. No. 3,884,857; U.S. Pat. No. 3,988,509; U.S. Pat. No. 4,248,990; and U.S. Pat. No. 4,252,924.
U.S. Pat. No. 3,239,370 discloses a random copolymerization of ethylene with an unsaturated carboxylic acid (e.g. acrylic acid) in a stirred autoclave operated at 16,000 psi, and 210.degree. C. using a peroxy initiator, the so-formed copolymer being particularly useful as a coating for non-metallic substrates.
U.S. Pat. No. 3,520,861 discloses a substantially homogeneous, compositionally uniform, random copolymer of ethylene/unsaturated acid (e.g. acrylic acid, methacrylic acid, crotonic acid) prepared in a continuous manner in a stirred autoclave at high pressure and elevated temperature, using a free-radical initiator (such as a peroxide). The temperature of the polymerization is disclosed as being in the range of about 120.degree. C. to about 300.degree. C., preferably about 150.degree. C. to about 250.degree. C. The pressure of the polymerization is disclosed as being in the range of at least 1000 atmospheres, preferably between about 1000-3000 atmospheres, esp. between 1100-1900 atmospheres.
Canadian Pat. No. 655,298 and its U.S. counterpart (U.S. Pat. No. 4,351,931) discloses homogeneous, compositionally uniform, random copolymers of ethylene and unsaturated carboxylic acids (e.g. acrylic acid) wherein said copolymer comprises at least about 90% by weight of ethylene with a melt index of 0.01 to 30 g/10 minutes. The copolymers are prepared in a well-stirred reactor at a pressure of at least 1000 atmospheres, at 90.degree.-280.degree. C., using a free radical initiator, while maintaining the ratio of monomers (ethylene/acid) in the range of 10,000/1 to 50/1 by weight, the process being performed continuously by feeding monomers in, while removing reaction mixture, are maintaining a constant reaction environment. U.S. Pat. No. 4,351,931 discloses reaction of such copolymers with diamines and polyamides to yield condensation polymers.
U.S. Pat. No. 3,658,741 discloses homogeneous copolymers of ethylene and unsaturated carboxylic acids and esters, prepared in the presence of a chain transfer agent, a free radical catalyst, a temperature between 100.degree. C.-300.degree. C. and pressure between 100 and 1000 atmospheres, using turbulent agitation; the reaction is said to take place in the vapor phase and prepares very low mol. wt. copolymers.
U.S. Pat. No. 3,884,857 and U.S. Pat. No. 3,988,509 disclose the preparation of copolymers, such as ethylene/acrylic acid copolymers in a continuous, high pressure, free-radical polymerization process, at 100.degree.-250.degree. C. and 1000-2500 atmospheres of pressure.
U.S. Pat. No. 4,248,990 discloses copolymers, e.g. ethylene/acrylic acid copolymers which are said to distinguish over the random copolymers of Canadian Pat. No. 655,298 and of U.S. Pat. No. 3,520,861 by virtue of being non-random. This non-randomness is said to be the result of operating the steady state, high pressure, stirred reactor at a pressure of from 0 to about 500 psi above, and at temperature of from 0.degree.-15.degree. C. above, that needed to maintain a single phase reaction mixture at the given concentration of copolymer in the reaction mixture and at the given acid comonomer content of the copolymer.
U.S. Pat. No. 4,252,924 discloses the preparation of non-random copolymers, e.g. ethylene/acrylic acid copolymers in at least two constant environment, stirred autoclaves in series, each using a single phase reaction mixture, but where each succeeding autoclave is maintained at a temperature of at least 30.degree. C. above that of the preceding autoclave.
U.S. Pat. No. 3,484,403; U.S. Pat. No. 4,018,733; and U.S. Pat. No. 4,132,690 disclose blends of polyamides with ethylene copolymers, along with compatibilizers.